1. Field of the Invention
The present invention provides a method for curing organopolysiloxane compositions. More specifically, the present invention provides a method for curing organopolysiloxane compositions which consist of a photosensitizer and an addition-curable organopolysiloxane containing a platinum-type catalyst by heating and by exposure to ultraviolet radiation or to an electron beam.
2. Background Information
It is known in the prior art that organopolysiloxane compositions can generally be cured by heating; refer to Japanese Pat. No. 35-13709 (No. 60-13709), No. 36-1397 (No. 61-1397) and No. 46-26798 (No. 71-26798). However, all of these methods require elevated temperatures and heating for long periods of time with the resulting drawback of low productivity. On the other hand, organopolysiloxane compositions which can be cured at room temperature or low temperatures by exposure to ultraviolet radiation or an electron beam; (refer to Japanese Kokai [Laid-Open] Pat. No. 50-61386 (No. 75-61386) (United Kingdom Patent Specification No. 1,433,461, published Apr. 28, 1976), No. 50-61486 (No. 75-61486) (U.S. Pat. No. 4,064,027, issued Dec. 20, 1977), and 55-125123 (No. 80-125123) have been developed due to recent demands for increased productivity and the increasing diversity of applications. However, these compositions have certain drawbacks including one or more of the following: a strong mercaptan odor, quite poor pot stability at room temperature, slow curing rates inappropriate for practical applications, and nonuniform curing in interior sections.
Various methods were examined by the present inventors in order to eliminate the preceding drawbacks with the resulting development of a method for curing organopolysiloxane compositions, including uniform curing in interior sections, by heating and by exposure to ultraviolet radiation or an electron beam for a short period of time at low temperatures.